The advantages of water bearings in relation to oil bearings are known, in particular in terms of pollution. In fact the function and maintenance of an oil bearing inevitably causes some of the oil used to be released into the environment.
However production of a water bearing is particularly difficult. The radial play between the inner and outer surfaces of the bearing is reduced to the order of 0.1 mm, which in particular requires the inner surface of the bearing to be machined with a tolerance of less than or equal to 5 hundredths or a millimeter, preferably 3 hundredths of a millimeter. The best tools currently available allow such machining precision.
There is also a need to overhaul existing machines by replacing their oil bearings with water bearings.
Currently this overhaul consists of grinding the surface of the shaft forming the inner surface of the bearing, to change from the tolerance required for an oil bearing (typically 50 hundredths of a millimeter) to that required for a water bearing (typically 5 hundredths of a millimeters). For this the shaft must be removed from the machine to transport it from the operating site of the machine to a workshop for grinding the surface with a suitable tool. Then once ground, the shaft is transported from the factory to the operating site before being refitted, whereupon the machine can resume its operation.
As well as the risks linked to transport of the shaft and problems linked to a fitting and refitting the shaft, the time during which the machine is not in operation is particularly long (of the order of several months). This represents a high cost for the operator which often prevents him from proceeding with such an overhaul.
To reduce the lost operating time, document FR-A-2938616 proposes a hoop intended for mounting on the shaft, preferably in situ, the outer radial surface of the hoop constituting the inner surface of the bearing.
However mechanical constraints resulting from clamping of such a hoop have the effect of deforming the geometry of the outer surface of the hoop, such that the machining tolerance of the outer surface of the hoop obtained in the workshop is lost. Furthermore since the shaft surface is machined to the tolerance required for an oil bearing, after clamping of the hoop on the shaft surface, the tolerance of the outer surface of the mounted hoop corresponds to the tolerance of the shaft surface i.e. 50 hundredths of the millimeter.